Lambard tyre LockNut missing

Few weeks back in May I took my car to Lambard Thabazimbi to fit a Tyre I had bought there. The attendent fitted the Tyre and did not put back the LockNut on my VW front Tyre as it is missing. Monday I recently took the car to the carwash and the boys tell me the LockNut is missing on that wheel. I go back to Lambard and management tells me they can't help me I must go buy new LockNut set. My spare compact at the boot has a nut spanner /bolt like written CRV..I asked them where that bolt is coming from as they was nothing for a Honda CR-V in my car. The manager says it's a long time and he cannot look into his camera and cannot help me. The last people to attend to the Wheel was Lambard Thabazimbi and now they are saying they don't know yet they changed the car Tyre ..my wheel is in danger of being plugged off by *********.